Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 40 years ago and resembles a phonograph. That is, the hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that spin at a standard rotational speed. A plurality of magnetic read/write transducer heads, for example, one head per surface of a disk, is mounted on the actuator arm. The actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly, e.g., the arm and head, is known as a head gimbal assembly (HGA)
In operation, the plurality of hard disks are rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk drive aligns a head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, refinements of the disk and the head have provided great reductions in the size of the hard disk drive. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are generally much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Refinements also include the use of smaller components and laser advances within the head portion. That is, by reducing the read/write tolerances of the head portion, the tracks on the disk can be reduced in size by the same margin. Thus, as modern laser and other micro recognition technology are applied to the head, the track size on the disk can be further compressed.
A second refinement to the hard disk drive is the increased efficiency and reduced size of the spindle motor spinning the disk. That is, as technology has reduced motor size and power draw for small motors, the mechanical portion of the hard disk drive can be reduced and additional revolutions per minute (RPM) can be achieved. For example, it is not uncommon for a hard disk drive to reach speeds of 15,000 RPM. This second refinement provides weight and size reductions to the hard disk drive and increases the linear density of information per track. Increased rates of revolution also provide a faster read and write rate for the disk and decrease the latency, or time required for a data area to become located beneath a head, thereby providing increased speed for accessing data. The increase in data acquisition speed due to the increased RPM of the disk drive and the more efficient read/write head portion provide modern computers with hard disk speed and storage capabilities that are continually increasing.
Particularly, with regard to data storage devices, these advances have attributed to increases in storage density. However, the increase in storage density has led to a weaker and/or smaller signal strength emitted by each data bit. This has required the development of read/write heads having increased sensitivity to the intensity of the signals emitted by the data bits. Those skilled in the art utilizing techniques for fabricating read/write heads are constantly searching for alternatives that provide increased sensitivity to the read/write head.
Specifically, within the read/write head fabrication and assembly process, once the read/write head wafer is fabricated and sliced, creating separate head sliders, there is a lapping process. The lapping process thins and polishes the head slider. This lapping process, in part, determines the flying height of the read/write head over the disk, the sensor dimension, and the sensitivity of the sensor.
Prior art FIG. 1 shows a conventional lapping environment 10 depicting a common lapping process 66 to be performed on a customarily fabricated and sliced read/write head wafer 15. Read/write head slider 15 includes a deposition surface 25 upon which the layers and components of the read/write head slider 15 are deposited. Read/write head 15 also includes a surface 20 upon which the lapping process 66 is performed. Surface 20 is commonly referred to as an air bearing surface and is the surface of the read/write head slider 15 that is most proximal to a data bearing surface of the platter upon which a data bit is stored. Slider 15 also includes a sensor 40 for sensing the charge state of data on a data storage device, e.g., a hard disk drive, and for affecting change in data charge state. Lapping process 66 is performed on surface 20 and sensor 40 as indicated by arrows 67. It is noted that conventional lapping processes, e.g., 66, are performed directly on sensor 40 as sensor 40 has been extended to contact surface 20 during fabrication.
However, because lapping process 66 is applied to sensor 40, the abrasive quality of lapping process 66 creates a layer material under stress of process 66 that can induce degradation of the magnetic sensor response. In many instances, this degradation can completely disable sensor 40, thus requiring new wafer fabrication. Further, lapping process 66 can also induce surface damage to sensor 40. Lapping induced surface damage is known to cause deadening of sensor 66, rendering the sensor incapable of detecting a charge state of a data bit. Further, by virtue of sensor 40 exposure, conventional lapping process 66 can contribute to electrostatic discharge (ESD), further reducing sensitivity of sensor 40.
Further, because of sensor 40 being comprised of one material, e.g., a single element or a composition of elements, there is no detectable resistance difference within the material comprising sensor 40. Thus, conventional lapping processes are resigned to utilize time of lap and rate of lap to control the lapping process.
A common solution to achieve a better lap is to cause a smoother (more precise) lapping process 66 that, while slower than a rough lap, can provide a finer lap. It is known that a smoother lap can consume a non-trivial amount of time to achieve proper lapping. Economically, at some point the result achieved with a smoother lap is overshadowed by the amount of time, e.g., cost, required to achieve the desired result.